Otis Elevator Company

Yasutami Kito

Kenji Oshima

Masao Iwasa

Kazuhiko Doi

Masayuki Mori

Failure detector for regeneration power absorbing means

An inverter control device for controlling an induction motor that drives elevators, has two induction motor coils that are electrically separate with inverters connected to each coil, and a control device that controls these two inverters with the same current command. The preferred structure is one where one control system outputs one current command to two inverters, the inverter control device has two separate control systems that divide one current command and output each half to the respective inverter and one carrier circuit that modulates each control system at the same timing, or two separate converters are connected to the power element of the respective inverters.

Inverter control device for driving an elevator

A clipper circuit includes an auxiliary diode connected between a capacitor and diode, themselves forming a clipper circuit. The auxiliary diode thus forms an auxiliary clipper circuit taking the capacitor as a common capacitor. The clipper circuit diodes shunt current from the capacitor into first and second currents through the diodes. This obviates the necessity for a snubber circuit and power source clipper circuit as employed in the prior art.

Clipper circuit for power transistor circuit and inverter circuit

An elevator starting compensation device for performing starting compensation with addition of a load detection signal and a torque command signal comprising a speed command circuit, an automatic speed regulator amplifier for outputting the torque command signal, and a load detecting element for detecting load of a passenger cage, characterized in that it further includes a static frictional torque compensating element inputting a load detection signal and travel (lifting and lowering) signal and outputting a static frictional torque compensation signal predetermined according to the magnitude of the sensed passenger load, the torque compensation signal being added to the torque command signal so that start-up of actual speed is not delayed with respect to the speed command.

Start compensation device for elevators

The present invention is achieved with a control unit for a PWM inverter for comparing (8) a voltage command signal (7) with the fundamental of the inverter's output voltage waveform and for comparing (11) the result with a carrier signal (10) and using that result to keep the output voltage waveform equal to the voltage command signal. The use of the output's fundamental for feedback eliminates the prior art need to use slight delays in the inverter's switching stage thereby removing the prior art torque ripple and consequent vibration problems particularly at low speed and furthermore enables smoother stopping and starting control using variable speed ranges of several hundred to one.

PWM inverter control unit

A multiphase multiplier circuit employs analog switches, each of which is duty controlled for multiplying input voltage signal with a multiplier determined depending on the duty cycle ON/OFF period. The multiphase multiplier circuit further includes means for multiplying a reference voltage signal by a desired factor for deriving the difference between the product and the factor for controlling duty cycles of the analog switches.

Multiphase multiplier

In an elevator provided with an inverter driven induction motor, output torque is determined by direct current of an inverter, slip frequency is determined from the thusly determined torque, the gap between an open-loop dictated speed pattern and the actual speed is compensated by the slip calculated during acceleration and constant speed movement, so that the open-loop control may be improved in terms of stop position precision.

Speed control system for elevators

A star-connected sensing resistor at the A.C. output side of a PWM inverter detects an output voltage across the resistor, a PWM control according to the invention then amplifies the detected voltage, compares the amplified voltage with a sine wave voltage command signal, amplifies the compared output in a P-I amplifier having a definite gain for a D.C. current, compares the P-I amplified output to a carrier and thus provides a PWM output for controlling the inverter.

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Tokyo, Japan

Yasutami Kito